#!/usr/bin/env python3
"""
This Script changes the monitor in KODI's guisettings.xml to the wanted output
according to the DISPLAY environment variable.
"""

import os
import sys
import subprocess
import xml.etree.ElementTree as ET


GUISETTINGS = '/var/lib/vdr/.kodi/userdata/guisettings.xml'
CACHE_DIR = '/var/lib/vdr/.kodi/.display_cache'
VIDEOSCREEN_TEMPLATE = """<settings version="2">
    <setting id="videoscreen.monitor" default="true">{}</setting>
</settings>"""


def get_output_names():
    """
    get display name from xrandr output for given DISPLAY environment variable
    """
    xrandr_output = [
        l for l in subprocess.check_output(
            ["xrandr"],
            env={"DISPLAY": os.environ["DISPLAY"]}
        ).decode("utf-8").splitlines()
    ]
    return [l.split()[0] for l in xrandr_output if " connected " in l]


def parse_template(template_path, template, output=""):
    """read videoscreen settings from backup or create a stub file"""
    try:
        xml_tree = ET.parse(template_path)
    except FileNotFoundError:
        print("{} not found, creating stub file".format(template_path))
        xml_template = ET.fromstring(template.format(output))
        xml_tree = ET.ElementTree(xml_template)
    finally:
        xml_tree.write(template_path)
    return xml_tree


def backup_videoscreen():
    """parse guisettings.xml for display name an backup videoscreen data"""
    tree = parse_template(GUISETTINGS, VIDEOSCREEN_TEMPLATE, "Default")
    root = tree.getroot()
    videoscreen = root.find("./setting[@id='videoscreen.monitor']")
    output = videoscreen.text
    xml_path = os.path.join(CACHE_DIR, '{}-videodevice.xml'.format(output))
    base_tree = ET.fromstring('<settings version="2"></settings>')
    xml_tree = ET.ElementTree(base_tree)
    backup_root = xml_tree.getroot()
    backup_root.insert(0, videoscreen)
    xml_tree.write(xml_path)
    print("written backup for {} to {}".format(output, xml_path))


def change_videoscreen(output, new_videoscreen):
    """change videoscreen node to content of backup file"""
    tree = parse_template(GUISETTINGS, VIDEOSCREEN_TEMPLATE, output)
    root = tree.getroot()

    videoscreen = root.find('./setting[@id="videoscreen.monitor"]')
    if videoscreen is not None:
        videoscreen.text = new_videoscreen.text
    else:
        videoscreen = root.find("./settings")
        root.insert(0, new_videoscreen)
    tree.write(GUISETTINGS)
    return tree

if __name__ == '__main__':
    output = get_output_names()[0]
    if not output:
        sys.exit("Error: no screen name found")
    try:
        os.makedirs(CACHE_DIR, exist_ok=True)
    except PermissionError:
        sys.exit("Error: insufficient permissions to create cachedir {}".format(
            CACHE_DIR))
    try:
        backup_videoscreen()
    except FileNotFoundError:
        print("{} does not exist".format(GUISETTINGS))
    except Exception as e:
        print("Could not backup videoscreen.monitor:", str(e))
    xml_path = os.path.join(CACHE_DIR, '{}-videodevice.xml'.format(output))
    videodir_xml = parse_template(xml_path, VIDEOSCREEN_TEMPLATE, output)
    videodir_root = videodir_xml.getroot()
    new_videoscreen = videodir_root.find("./setting[@id='videoscreen.monitor']")
    guisettings_xml = change_videoscreen(output, new_videoscreen)